div{
    box-sizing: border-box;
    border: 1px solid red;
}
.box1{
    width: 200px;
    height: 200px;
    background: red;
    display: flex;
    .box1-1{
        width: 50%;
        height: 100%;
    }
    .box1-1-1{
        height: 50%;
        background: blue;
    }
    .box1-1-2{
        height: 50%;
        background: yellow;
    }
    .box1-2{
        flex: 1;
        background: pink;
    }
}